Metal materials were used to replace, strengthen and repair human organs and tissues earlier. These materials should not only meet certain requirements of strength, wear resistance and fatigue resistance, but also have biological functions and physiological compatibility (such as non-toxic, no pathological changes in human tissues), and have sufficient corrosion resistance to various body fluids in the human body. Metal biomedical materials mainly include stainless steel, cobalt-chromium alloy and titanium alloy. Among them, stainless steel and titanium alloy have the best physiological compatibility. Such as artificial heart valves, spinal rods and skulls (platinum, titanium and zirconium alloy plates). In addition, silver-tin alloy, cobalt-chromium alloy and nickel-chromium alloy are used for tooth restoration and correction.
Second, smart materials.
Intelligent material refers to the implantation of sensors, signal processors, communication and controllers, actuators in materials or structures, so that materials or structures have intelligent functions and life characteristics such as self-diagnosis, self-adaptation and even self-healing of damage. For example, the condition monitoring of buildings, bridges, dams, power stations, airplanes, etc. Self-adjustment of vibration and shape, self-repair of damage, etc. Generally speaking, once metal materials are fatigued and damaged in the process of use, it means that they are eliminated and replaced, and there is no self-feeling and recovery function similar to that of organisms. Through special treatment, it is endowed with the function of damage early warning, and the damage can be repaired, so the material has the characteristics of "intelligence". If boron particles are compounded into aluminum alloy, when the alloy is damaged, it will emit sound waves, and the sound transmitter will receive the signal and immediately issue an early warning.
Third, low-dimensional functional materials
Compared with large-scale three-dimensional materials, low-dimensional functional materials can be divided into two-dimensional materials (film materials), one-dimensional materials (fiber materials) and zero-dimensional materials (nano materials).
Thin film materials (such as diamond films) have developed rapidly in recent years and have a wide range of potential uses because of their special physical and mechanical properties. Due to resource and price factors, its practical application is greatly limited, but at present, this once considered extremely scarce material can only be produced by ordinary equipment. With the development and application of rapid quenching technology of molten metal, chemical vapor deposition (CVD), physical vapor deposition (PVD) and other preparation technologies, thin film materials have developed rapidly. In the information age, metal thin film materials used for information recording and storage have become a very active research field in recent years. For example, the magneto-optical disk, which came out in 1985, can be read, written and erased repeatedly. It is a device that uses magnetic thin films to store optical information.
A large number of metal fiber materials are used as reinforcing agents and structural materials of composite materials (such as glass fiber, carbon fiber, polymer fiber and optical fiber). In recent years, with the development of ceramic-based and metal-based materials, people have developed metal whiskers (that is, linear metal crystals with a diameter of micron or less) and oxide whiskers (such as Al2O3).
Nano-materials belong to zero-dimensional materials, and their grain size is generally less than 100nm, which can be as low as several nm. One of their characteristics is that the surface is extremely developed, and the atoms in the surface layer account for a high proportion of all atoms, so they have many extremely special properties. The electromagnetic properties of nano-metal powder have changed greatly, such as ferromagnetism, paramagnetism, low temperature insulation and so on. The reflective ability of metal nanoparticles to light can be reduced to 1%, and it becomes almost blackbody. Based on this, stealth materials with high electromagnetic wave absorption rate and extremely low reflectivity have been developed for aircraft to avoid radar detection and tracking. Nano-material is a new material with great application potential.